Homemade Cinnamon-Cherry Fizz Follow Up The First

After 4 days I've finally gotten a bit of carbonation out of the batch of Cinnamon-Cherry Fizz I made.
The first two tester bottles I opened(the first after 48 hours, the second after 72) had no fizz and slight fizz(respectively), and excellent cinnamon flavor-but no cherry flavor that I could detect. That might come out in the refrigeration though, so we'll see.
This morning, however, I checked a third bottle and was greeted with a slight bubble-rush to hint towards the slight bit of carbonation that was already present. Last time this happened I waited 12 hours and popped the bottles in the fridge to be met with a perfect amount of fizz upon letting it stand.
This will be another two part follow-up, as I will definitely revisit, review and add my thoughts about improving the batch if necessary. However, this batch has given me some new information. I have previously made mention of fiberglass-flavors in sodas. I always thought the culprit was too much cinnamon, or it's chemical reaction with the yeast, however, I'm now thinking it is almost exclusively the fault of the yeast.
I made my cream soda from scratch and ended up with that funky fiberglass taste, although in smaller doses then my first attempt. I also used my champagne yeast for that. Lo and behold, I made a quickie batch of cream soda from extract for my wife(whom didn't care for my homemade root beer at all), and used the rest of the champagne yeast. It never carbonated. Which leads me to believe that the fiberglass flavor in my homemade sodas of the past has come from "spoiled" yeast. If it's at the end of it's shelf life, it may produce some weird flavors in combination with it's ingredients. Considering I used the same exact yeast a mere week after the previous batch(which carbonated just fine, but with weird off-flavors), I'm thinking the yeast was at the end of it's viability-it may have been expired(I cut the expiration date off opening the package).
The first cause of off-tasting beverage is generally spoilage brought on by bacteria from improperly sanitized bottles/equipment. However, I did a thorough job of that on my cream soda, and had on the 3 previous batches I had made that I recalled getting the off-flavor with.
Long story short-make sure your yeast is fresh and used within a month of opening it.
Considering I had no off-flavors with this batch(which consists mainly of cinnamon-and lots of it), I can safely say that cinnamon is not the culprit-and thank goodness for that-cinnamon is tasty.

Recipe: Homemade Cinnamon-Cherry Fizz